This invention relates to a process for making non-hydrolytic surfactant capped nanocrystals. More particularly, it relates to a process for making non-hydrolytic surfactant capped nanocrystals of transition metal oxides using a single precursor approach, and to the nanocrystals made thereby.
The advent of new methods to prepare semiconductor and metal nanocrystals, specifically the injection of molecular precursors into hot organic surfactants, has yielded markedly improved samples with good size control, narrow size distributions, and good crystallinity of individual and dispersable nanocrystals.1-3 It is of considerable interest to apply these methods to the synthesis of transition metal oxide nanoparticles, which typically are prepared by methods involving water as solvent or reactant.4-9 Using nonhydrolytic preparations of metal oxide nanocrystals at high temperature in organic surfactants, one observes markedly different properties with respect to defect structure and surface composition. So far, there has been only one example of the solution-based nonhydrolytic synthesis of individual TiO2 nanocrystals.10 Metal oxide nanocrystals with nonhydroxylated surfaces are believed to have significant advantages for applications in catalysis, ceramics, energy storage, magnetic data storage, sensors, ferrofluids, etc.
The following references contain useful background information pertaining to this invention.
1. Murray, C. B.; Norris, D. J.; Bawendi, M. G. J. Am. Chem. Soc. 1993, 115, 8706-8715.
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3. Sun, S.; Murray, C. J. Appl. Phys. 1999, 85, 4325-4330.
4. Charles, S. W.; Popplewell, J. Ferromagnetic Materials; Northholland Publishing Co.: Amsterdam, N.Y., Oxford, 1982; Vol. 2.
5. Brinker, C. J.; Scherer, G. W. Sol-Gel Science; Academic Press: San Diego, 1990.
6. Ziolo, R. F.; Giannelis, E. P.; Weinstein, B. A.; O""Horo, M. P.; Ganguly, B. N.; Mehrotra, V.; Russell, M. W.; Huffman, D. R. Science 1992, 257, 219-223.
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9. Ying, J. Y. Special Issue: Sol-Gel Derived Materials. In Chem. Mater. 1997, 9, 2247-2670.
10. Trentler, T. J.; Denier, T. E.; Bertone, J. F.; Agrawal, A.; Colvin, V. L. J. Am. Chem. Soc. 1999, 121, 1613-1614.
11. Comprehensive coordination chemistry: the synthesis, reactions, properties and applications of coordination compounds, 1st ed.; Pergamon Press: Oxford, England, 1987; Vol. 2, Chapter 15.9.2.
12. Helm, D. v. d.; Merritt, L. L.; Degeilh, R.; MacGillavry, C. H. Acta Crystallogr. 1965, 18, 355-362.
13. Elerman, Y.; Atakol, O.; Svoboda, I.; Geselle, M. Acta Crystallogr. C 1995, 51, 1520-1522.
14. Tamaki, K.; Okabe, N. Acta Crystallogr. C 1996, 52, 1612-1614.
15. Kellner, R.; Prokopowski, P. Anal. Chim. Acta 1976, 86, 175-184.
16. Nolze, G.; Kraus, W. Powder Diffr. 1998, 13, 256-259.
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It is an object of this invention to provide a non-hydrolytic process for the preparation of transition metal oxide nanocrystals.
It is a further object of this invention top provide a non-hydrolytic process for the preparation of transition metal oxide nanocrystals having non-hydroxylated surfaces.
It is a still further object of this invention to provide new and novel transition metal oxide nanocrystals.
These, and other objects are achieved by injecting a solution of a metal cupferron complex of the formula M Cup, wherein M is a transition metal, and Cup is a cupferron, into an amine based coordinating surfactant, the injection reaction being conducted at a temperature ranging from about 250 to about 300xc2x0 C., for a period of time sufficient to complete the reaction.